Conventionally, for example, Patent Document 1 discloses a control apparatus for a cylinder cut-off type engine which can switch an operation between a full cylinder operation in which all cylinders are operated, and a cylinder cut-off operation in which drive of intake and exhaust valves of some of the cylinders is stopped to halt the some of the cylinders. In the conventional control apparatus, how many times the engine revolves during a cylinder cut-off operation is counted, and when the number of the counted revolutions reaches a predetermined value, the operation is temporarily returned to the full cylinder operation. In the above described conventional control apparatus, deterioration of exhaust emission at the time of return to the full cylinder operation due to oil ascent in the halted cylinders is prevented by the control like this.
The applicant recognizes the documents described as follows including the above described document, as the documents relating to the present invention.